An amino acid from tea, studied for calm focus, particularly alongside caffeine.
L-Theanine is an amino acid best known from tea leaves, studied for promoting a calm, focused mental state without sedation.
Much of the research on L-Theanine specifically examines it in combination with caffeine — worth noting since this formula is marketed as non-stimulant and caffeine-free.
On its own, without caffeine, L-Theanine's evidence for cognitive enhancement is more modest than the caffeine-paired research suggests.